1. Field of the Invention
The invention relates generally to methods and apparatuses for improved visualization and reading of electrophoresis gels. In particular, the invention relates to a system and methods for straightening an electrophoresis gel image and analyzing electrophoresis gels following electrophoresis of biological materials. The invention further relates to a system and methods for automatic analysis or autogenotyping of electrophoresis gels following straightening of the gel image.
2. Background of the Related Art
Electrophoresis is an extremely important and widespread technique in biological research, biotechnology, and medical and agricultural sciences. The technique relies on the migration or movement of charged molecules through a solid matrix in an electric field, and is especially applicable to the analysis of biological polymers, and in particular, to proteins and nucleic acids (RNA and DNA) . Thus, electrophoresis is widely used for a broad range of purposes, including: nucleic acid sequencing, diagnosis of genetic diseases, as well as DNA fingerprinting in forensic medicine, paternity/maternity testing, and identification of disaster victims.
During electrophoresis, the distance migrated through the electrophoresis matrix by a molecular species is dependent on a number of factors, including: the size of the molecule, the net charge on the molecule, and the strength of the electric field. The distance migrated is inversely related to molecular size, i.e. the larger the molecule the smaller the distance migrated. Therefore, electrophoresis of a number of molecules, or DNA fragments, of different sizes results in a corresponding number of bands located at a range of different distances along the gel.
Each band of DNA represents multiple copies of a DNA fragment of a particular size (i.e. of a particular number of nucleotides). The fact that DNA fragments having different numbers of nucleotides or base pairs possess different electrophoretic mobilities, forms the basis for all separations and analyses of DNA and DNA fragments by electrophoresis.
In order to determine the size (or number of nucleotides, expressed as base pairs, bp) of a DNA fragment in a particular band of an electrophoresis gel, it is necessary to include a number of DNA standards in one or more lanes of the electrophoresis gel.
DNA standards are fragments of DNA of known size. Comparison of the distance migrated by the DNA standards with the distance migrated by a DNA fragment to be analyzed, allows for the calculation of the size of DNA fragments to be analyzed. Thus, by the use of standards, distances migrated by the various bands of the DNA to be analyzed can be assigned to a particular molecular size or number of bp. In fact typically, a mixture of a number of different sized standard molecules are run on an electrophoresis gel to provide a series of bands, or a ladder, in which each band or rung of the ladder represents a known molecular size.
One problem with electrophoresis gels, which impairs manual reading and analysis of the gel image, and which prevents accurate automatic analysis by a device, such as a computer controlled device, is that the bands are irregularly or imperfectly formed during electrophoretic migration. For example, it is frequently the case that one or more bands in one or more lanes of the gel are curved or crooked. Consequently, two identical molecules or DNA fragments having the same number of base pairs, and in adjacent lanes of the gel may not be perfectly aligned and may show somewhat different distances of migration. Such aberrations in an electrophoretic image are particularly common at the edges of the gel.
Another common problem in analyzing electrophoresis gels is the tendency of one or more bands to appear faint or indistinct.
Due to the high throughput and immense numbers of electrophoretic analyses currently being performed world-wide, there is tremendous long-felt need for a system that can rapidly, reliably and reproducibly perform automatic analysis of electrophoresis gels.